An internal combustion engine operates when sparks are applied by spark plugs to a homogenous air and fuel mixture in the combustion chambers of the engine. After application of the spark to the mixture in the combustion chambers, the sparks ignite the mixture, causing the engine to rotate the crank shaft of the engine. The spark energy is generated by an ignition coil and the time that the current is applied to the ignition coil primary is usually referred to as the dwell or on-time of the ignition coil primary.
Ignition systems may be divided into inductive ignition systems and capacitive discharge ignition (CDI) systems. Inductive ignition systems can further be divided into distributor systems and distributor-less (DIS) systems.
In an inductive, distributor-based system, energy is stored in the coil primary inductance and transferred to a coil secondary inductance and then to the spark plugs for each of the cylinders of the engine. At low speeds, the energy stored in the ignition coil is totally discharged to effect the spark. However, at high speeds, residual energy typically remains stored in the ignition coil even after the spark is discharged. Since distributor-based systems only have a single coil, they can only fire the spark plugs every 90 degrees of crankshaft rotation. Thus, with an 8 cylinder engine, 720 degrees is needed to fire all of the cylinders in the engine.
In a DIS system, multiple ignition coils are used to deliver energy to the spark plugs of the cylinders of the engine. This setup may also include using multiple ended coils, for waste spark DIS, of the same coil to deliver energy to different spark plugs. In waste spark DIS systems, a spark is fired once every 360 degrees. In some coil-per-cylinder DIS, no waste spark is used firing the coil/plug once every 720 degrees. Since a spark is not fired as often in DIS systems as in distributor-based systems, all of the energy from the coil is transferred to the spark plugs before the next ignition cycle begins. In other words, with each ignition cycle, there is no energy remaining in the ignition coils and the ignition coil current begins ramping from a value of zero amperes. In addition, since no residual energy storage occurs in DIS systems between cylinder firings, simple fixed ontime dwell control is usually used in such systems.
In CDI systems, a battery voltage is stepped up to over 400 volts and the energy is stored in a capacitor. The capacitor stored energy is charged by the battery voltage to be later discharged in the ignition coil primary to generate a spark from the ignition secondary to the spark plug. A CDI system may use single or multiple ignition coils. Dwell time control is not provided in CDI systems.
Ignition systems can be coupled to various types of devices. For example, traction control devices are often used to control traction of the vehicle and can be connected directly to the ignition coil of the engine or the ignition mag-input. Traction control devices adjust the operation of the engine so that when the vehicle loses traction, the driver can regain control of the vehicle. Although valuable in normal passenger driver applications, traction control devices are forbidden in most high-speed racing applications, since they give an unfair advantage to drivers employing these devices.
Previous distributor-based, single ignition coil systems are incapable of effectively managing the energy stored in the ignition coil for all speeds of the engine using dwell control. When dwell control was attempted at all, it was made imprecisely and/or was incapable of controlling a high current ignition coil with low inductance and high energy storage and low power dissipation at high power levels under all operating conditions. Consequently, these previous systems could not effectively manage the stored energy or residual energy of the coil at lower speeds and, at the same time, provide the full stored energy needed by the engine at higher speeds. Undesirable consequences often occurred in previous systems, for instance, the burning out the ignition coil at some speeds and the inability to provide the proper energy at other speeds of operation.